Technical Field of Invention
The invention disclosed and taught herein relates generally to a system and method for use in floating offshore environments including drilling rigs. The embodiments described below related generally to the design layout of equipment used on a subsea wellhead system or subsea tree system related to an environmental containment system for the same.
Description of Related Art
In the offshore drilling environment, pollution from in-hole work being performed is an environmental concern. For example, in plugging and abandonment (P&A) operations, it is important to ensure contaminates such as hydrocarbons, oil based muds, and hazardous brines are not unintentionally released to the environment. When a well barrier is removed in open water operations, there is a chance that a small amount of trapped hydrocarbons or contaminates could be released into the ocean. This typically would not be associated with sustained flow from the well.
Upper abandonments are typically performed with a riser based subsea blowout preventer stack (BOP) or Intervention Riser System (IRS). The riser is a conduit that enables tools and fluids to be passed from the surface rig to the subsea well. This provides a physical barrier to the environment. In some cases, the upper abandonment of a well entails the removal of the upper sections of tubing and casing strings. The outside diameter of these strings and associated hangers often prohibit the use of an IRS. The work can be performed without the use of a riser (riserless), but other means of environmental barriers must be used in place of the riser. Therefore, a need exists to provide method and system to meet this objective. Prior to performing an upper abandonment, the hydrocarbon bearing production zones will have been sealed with cement plugs. In current practice, at least two tested barriers will have been placed in full compliance with local regulations.